'Tis the season for aggressive marketing campaigns. After Amazon went after Apple's jugular over the iPad mini, Microsoft is going after Google's integrity with its latest ad campaign.

Bing just launched a national campaign to highlight its commitment to honest search results and to help explain to consumers what it calls the "risks of Google Shopping's newly announced 'pay-to-rank' practice."

Bing says Google shows shopping search results that are not true search results like they would see elsewhere on Google. According to Bing, the results are actually ads that are ranked, in part, by who pays the most. Google could not immediately be reached for comment.

Microsoft's Allegations

In recent weeks leading up to Black Friday and Cyber Monday, Microsoft alleges that Google quietly changed its shopping results from "Google Product Search," which represented fairly comprehensive results for products and merchants across the Web, to a pay-to-rank model called "Product Listing Advertising."

"Merchants must now pay Google to be listed in the shopping results, and how much they pay helps determine how they appear in the rankings, so now every 'result' is really just an ad. This new policy means consumers are getting Scroogled," Bing said.

That, said Microsoft, is an issue for shoppers who visit the site they have used for years, conduct what they think is a "search," and get a set of rankings that look like the objective results Google delivers everywhere else.

Meanwhile, Bing continued, the lawyers at Google Shopping are now calling results "listings." Microsoft complains that Google even call out, nontransparently hidden behind a disclaimer or buried in a footer, "Payment is one of several factors used to rank these results."

Pinging Google's Integrity

"Instead of showing you the most relevant shopping search results for the latest coffee maker you're looking to buy mom, Google's new redesigned shopping vertical now decides what to show you -- and how prominently to display what product offers they show -- based partially on how much a merchant selling the product has paid Google," Microsoft said. "Merchants can literally pay to improve their chances to display their product offers higher than others inside of Google's shopping 'search,' even if it's not necessarily better or cheaper."

Microsoft went on to decry the injustice of this alleged lack of transparency. Microsoft argued that such practices are not what consumers expect from search and it's not how the company thinks search engines should help consumers get the best prices and selection when shopping.

We asked Greg Sterling, principal analyst at Sterling Market Intelligence, for his take on Bing's "Don't Get Scroogled" campaign. He told us this is obviously a PR move to call Google out as deceptive or hypocritical.

"It probably won't generate much new usage for Bing but it may put another, incremental dent in Google's reputation," Sterling said. "There is some paid inclusion in Bing's shopping site, though most of the results are 'organic.' "